1. Field of the Invention
This invention relates to an ignition timing controller for a multi-cylinder internal-combustion engine. It is capable of delaying ignition timing for each of the multiple cylinders upon the detection of knocks in the individual cylinders of the multicylinder internal-combustion engine.
2. Description of the Prior Art
Ignition timing controllers are disclosed in, for example, Japanese patent unexamined patent publication Nos. 58-53675 and 58-165574.
A known ignition timing controller delays ignition timing for a particular cylinder when that cylinder is detected to be knocking. It delays ignition timings for all cylinders, without regard to which of them may be knocking when the intensity of engine knock or the frequency of engine knock exceeds a predetermined level. This allows the engine to deal quickly with a critical operating condition such as, for example, acceleration, during which knocking is likely to occur.
Although such an arrangement can respond quickly to a knocking problem, it has some operational drawback. It is possible that knocking occurs substantially continuously in a particular cylinder, rather than in all cylinders of the internal combustion engine. It may be that the knock intensity of a particular cylinder may be very high, even though the knock intensity of the other cylinders may be low. When ignition timing is indiscriminately delayed for all cylinders under such conditions, certain cylinders are retarded that should not be. This deteriorates engine performance.